title: Brain levels of the neurotoxic pyridinium metabolite HPP+ and extrapyramidal symptoms in haloperidol-treated mice.
abstract: The typical antipsychotic haloperidol is a highly effective treatment for schizophrenia but its use is limited by a number of serious, and often irreversible, motor side effects. These adverse drug reactions, termed extrapyramidal syndromes (EPS), result from an unknown pathophysiological mechanism. One theory relates to the observation that the haloperidol metabolite HPP+ (4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]-pyridinium) is structurally similar to MPP+ (1-methyl-4-phenylpyridinium), a neurotoxin responsible for an irreversible neurodegenerative condition similar to Parkinson's disease. To determine whether HPP+ contributes to haloperidol-induced EPS, we measured brain HPP+ and haloperidol levels in strains of mice at high (C57BL/6J and NZO/HILtJ) and low (BALB/cByJ and PWK/PhJ) liability to haloperidol-induced EPS following chronic treatment (7-10 adult male mice per strain). Brain levels of HPP+ and the ratio of HPP+ to haloperidol were not significantly different between the haloperidol-sensitive and haloperidol-resistant strain groups (P=0.50). Within each group, however, strain differences were seen (P<0.01), indicating that genetic variation regulating steady-state HPP+ levels exists. Since the HPP+ levels that we observed in mouse brain overlap the range of those detected in post-mortem human brains following chronic haloperidol treatment, the findings from this study are physiologically relevant to humans. The results suggest that strain differences in steady-state HPP+ levels do not explain sensitivity to haloperidol-induced EPS in the mice we studied.
authors.affiliation: Center for Psychiatric Genomics, Department of Genetics, University of North Carolina at Chapel Hill, NC, USA. Electronic address: crowley@unc.edu.
authors.forename: James J
authors.initials: JJ
authors.lastname: Crowley
authors.forename: Mehdi
authors.initials: M
authors.lastname: Ashraf-Khorassani
authors.forename: Neal
authors.initials: N
authors.lastname: Castagnoli
authors.forename: Patrick F
authors.initials: PF
authors.lastname: Sullivan
mesh_terms: D000818:Animals; D014150:Antipsychotic Agents / Q000633:toxicity*; D001480:Basal Ganglia Diseases / Q000139:chemically induced* / Q000503:physiopathology; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002853:Chromatography, Liquid; D004195:Disease Models, Animal; D006220:Haloperidol / Q000633:toxicity*; D008297:Male; D008409:Mastication / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D010636:Phenols / Q000737:chemistry / Q000378:metabolism*; D020005:Propanols / Q000737:chemistry / Q000378:metabolism*; D013045:Species Specificity; D018709:Statistics, Nonparametric; D053719:Tandem Mass Spectrometry
chemical_list: D014150:Antipsychotic Agents; D010636:Phenols; D020005:Propanols; C417567:3-(4-hydroxyphenyl)propanol; D006220:Haloperidol
keywords: Adverse drug reaction; HPP+; HPTP; Haloperidol; Mouse; Tardive dyskinesia